Means for expanding a received pulse radio signal



March 13, 1951 A. A. VARELA MEANS FOR EXPANDING A RECEIVED PULSE RADIO SIGNAL 2 Sheets-Sheet 1 Filed Oct. 27, 1958 9% e v r W TWW N. E A w h r W T A TTORNE Y March 13, 1951 A. A. VARELA MEANS FOR EXPANDING A RECEIVED PULSE'RADIO SIGNAL 2 Sheets-Sheet 2 Filed Oct. 27, 1938 INVENTOR Arthur A. T/arl 0. av

ATTORNEY Patented Mar. 13, 1951 MEANS FOR EXPANDING A RECEIVED PULSE RADIO SIGNAL Arthur A. Varela, Washington, D. 0. Application October 27, 1938, Serial N0. 237,222

16 Claims. (01. 2508) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This invention relates to means for producing an output of relatively high power and long duration in comparison with the power level and duration of a radio pulse signal of extremely short duration.

Among the several objects of this invention are:

To provide radio receiver circuits whereby a very short received signal may be expanded into an output signal persisting for a relatively long time after cessation of the received signal;

To produce an output of considerable power in response to a received signal of low power;

To convert a signal of very high frequency and extremely short duration into a response at audio frequency and of appreciable duration.

In the drawings:

Fig. 1 depicts schematically one form of my invention;

Fig. 2 shows by graphs the relative duration of a received pulse and the response produced thereby, together with certain voltage relations involved;

Fig. 3 shows schematically a further embodiment of the present invention wherein the energy in the system is twice rectified.

The present invention is adaptable to all frequency bands and to wire telegraph communication, but has particular application in high fret quency radio communication and control in which it is desired to use very low power in the transmitter and simple transmitting equipment.

My invention has further application in extending the upper frequency limit of communication with superfrequency negative grid transmitters in that oscillation in the transmitter exists during only a very small fraction of the operating time and therefore anode voltages of unusually high value may be employed with consequent reduction of electron transit time within the tubes, thus permitting operation at very high frequencies.

The transmitter utilized in connection with this invention sends a single pulse of very short dura tion to signal a dot and three evenly-spaced similar pulses to signal a dash. The frequency of the receiver output may be adjusted to give an audio note of any desired frequency by adjusting the frequency of an output oscillator, to be described hereinafter, and the duration of the output signal in response to a three pulse signal is substan tially three times as long as the response to a single pulse. Since the'duration of the transmitted pulse maybe of. the order of onemicro second or less the effective gain of this system over conventional means is enormous.

This invention has some points of similarity to that set forth in my co-pending application Serial No. 237,221, filed October 27, 1938. The principal advantage of the system herein described over that forming the subject of my said co-pending application lies in the higher power gain. Also, the present system may be used at low radio frequencies, where the system of my said co-pending application would not be desirable.

Transmitters adapted for used with this invention are described in the application of R. M. Page, Serial No. 223,503, filed August 6, 1938, now Patent No. 2,541,092 issued February 13, 1951. The only adjustment of such transmitters necessary to make them usable with thisinvention is that the pulsing rate of the transmitter be fixed so that one pulse is transmitted for a dot and three for a dash.

Briefly stated, the receiver shown in Fig. 1 consists of a self-quenching oscillator in which oscillation is initiated by the received pulse. During oscillation this oscillator produces a reduced bias on a second oscillator operating at audio frequency, thereby causing the second oscillator to, cut elf after quenching of the first oscillator is delayed by energy accumulated in a condenser, the discharge of which toefiect the desired result is produced by a diode valve. A series of recurrent pulses of proper time interval will therefore maintain the audio oscillator in a state of oscillation for a time proportional to the number of pulses received in the series.

The input to Fig. 1 is shown as a dipole 4, although it may be the output of any conventional amplifying means. The input is coupled to tuned grid circuit 5 which is in turn tightly coupled to tuned plate circuit 6, the tuned circuits re-. spectively including the grid 1 and anode 8 of vacuum tube 9. The circuit 5 will obviously be tuned to the frequency of the signal to be received and the circuit 6 will likewise be tuned to that frequency to constitute, with tube 9 and other elements, an oscillatory network. Voltage divider It is adjusted to bias grid 1 to a point that is just below the value of grid bias at which oscillations begin. Resistor II in series with cathode i2 is of such value as to prevent continuous oscillation after the received signal has ceased and capacitor 62 is connected across resis-- tor II and is of such value that it delays the quenching of oscillation for the desired time interval but gradually builds up to such potential that oscillations are extinguished.

Anode I3 of rectifier I4 is connected to the high potential side of resistor H to be set into operation by the potential there developed during oscillation and the cathode l of rectifier i4 is connected to control grid 16 of vacuum tube i1. Tuned plate circuit I8 is connected to anode 13 of tube H and is coupled with circuit to constitute an oscillatory system, the values of the elements in circuits l8 and 23 being such that their output is within the audio range. The fixed bias on grid 16 is derived from voltage divider 22. Connected in parallel between grid ;l6 and voltage divider 22 are the capacitor 23 andre'sistor 24, the value of resistor 24 being much higher than the effective resistance of diode l4 while the latter is passing current, and therefore the time of discharge of capacitor 23 throughresistor 2 6 is considerably longer than the time during which current is passing through the diode M to charge capacitor 23. The effective bias '01:! grid l6 does not follow the voltage on capacitor 23 but is held to a fairly constant value'by resistor 25 and capacitor 26 in parallel with each other and in series with cathode 21. The anode supply 28 and bypass capacitors 29 and 30 are conventional.

The operation of the system above described may be explained in connection with Fig. 2. A signal *pulse impressed upon tuned input circuit 5 is represented by the sharply peaked curve P, the small time period occupied by the pulse being indicated by the shortness of the base. When the pulse voltage reaches the value c at time To tube '3 begins to oscillate and capacitor 23 begins to charge as shown by curve a and audio oscillator tube I1 begins to operate. At the time designated T1 sufficient bias has been built up on capacitor 62 to extinguish the oscillati'o'ns'in tube 9 and capacitor 2-3 then begins to discharge with its potential following the curve b and when this potential has dropped to thevalue represented by the dashed line e1, at time T2, the tube ll-ceases to 'oscillate at time T2. This is the condition when -a single pulse, representing a dot, is received. It is apparent from Fig. 2 that the duration of the received pulse is short compared to time ToT1, and that this time is short compared to time T1-T2. Itis to be understood that these values are not to scale, since the pulse duration may be one microsecond while"TuT1'may be 0.005 second.

However, if *a-dashis being transmitted asecond pulse P2 is received and the operating voltage e on grid 1 is reached before the potential of capacitor '23 has dropped to the value c1, and therefore the audio oscillator is maintained in operation through-the time of a second discharge of capacitor 23. It "is obvious that so oftenas a new pulse is received before the potential of capacitor "23 drops to value er, the tube I! will continue in "uninterrupted oscillation, and hence the reception of three pulses, representing a dash,'would mean merely adding another pulse and discharge curve to Fig. 2. Thus, the audio frequency signal in phones 3| for a dash would have substantially three times the duration for a clot.

The system shownin Fig. 3 provides greater facility of tuning and the first oscillator is not self-quenching, but otherwise the action of the two systems is very similar. Here the tuned input circuit 32 is connected "to anodes 33 of a full wave rectifier 34, whereof the cathodes 35 are connected to grid 36 of oscillator tube 31. The oscillatory network of this tube includes tuned circuit 38 connected to anode 39 and a further tuned circuit li) connected to additional grid 41.

The rectifier 34 is biased against operation below a predetermined signal level through connection 42 to voltage divider 43 and the bias on grid 36 is derived through connection 44 to the voltage divider.

Upon reception of a signal and passage of current through rectifier 34 the capaciotr 65 in parallel with resistor 46 between cathodes 36 and grid 36 on the one sicie and voltage divider on the other, becomes charged and after cessation of current through the rectifier 34 the energy stored in capacitor 45 discharges through resistor 46 and maintains the tube 3? in oscillatory condition for atime longer than the duraup on capacitor 56 across resistor 51 by current through rectifier 50 :has dropped below a predetermined value. Again, the value of resistor 5'! is large incomparison'with the effective resistance of rectifier so while passing current, and therefore the discharge of capacitor 56 through resister '5! is longer than the time of charging capacitor 56, and :hence the duration of oscillations in audio oscillator tube 54 is longer than the duration of oscillations in tube :31. The oscillatory-netw'ork :of tube '54 includes tuned circuit 58 connected to anode 59 and tuned :circuit 60 connected:to additionalgrid'fi l. The audio output isqoerceptible by use'of phones 3i. It is thus apparent that'the very high frequency pulse of extremely short duration is twice expanded in length and a response :of audio frequency and or perceptible duration is derived, and that the time of the audio responsemay be varied to indicate either a dot or a dash.

The invention herein described and claimed may be used and/ormanufactured by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. #A :method of .radio communication, comprisirigthe steps offreceiving a signal pulse, applying said :pulse "to initiate electric oscillations with transfer of energy while said oscillations persist, utilizing a portion of the said transferred energy to' build 'up gradually a potential that extinguishes said oscillations after a predetermined time, rectifyinganother portion of said energy, and utilizing said rectified energy to initiate and maintain other electric "oscillations for a time'longer than said predetermined time of duration of the first oscillations.

2. A method of radio communication, comprising the steps of receiving a train of signal pulses wherein the time between two succeeding pulses is-longcompared'with the duration of one pulse, applying each-said pulseto' initiate electric oscillations'withtransfer of energy while said oscillations persist,'utilizing a portion of thesaid transferred energy to build up a potential that extinguishes'saidbscillations after a substantial'portion of the time betweentwo succeeding pulses, rectifying another portion of said energy. and

utilizing -said rectified energy to initiate and 3. A method of radio communication, comprising the steps of receiving a train of signal pulses wherein the time between two succeeding pulses is long compared with the duration of one pulse, rectifying the full waves in each said pulse, applying the rectified energy to initiate first electric oscillations and to store energy to maintain said oscillations for a time long in comparison with the duration of a pulse with transfer of energy while said oscillations persist, applying and storing the said transferred energy to initiate second electric oscillations and to maintain said second oscillations for a time longer than the duration of said first oscillations.

4. A method of radio communication, comprising thesteps of receiving a train of signal pulses wherein the time between two succeeding pulses is long compared with the duration of one pulse, rectifying at least a portion of the energy in each said pulse, applying the rectified energy to initiate first electric oscillations and to store energy to maintain said oscillations for a time long in comparison with the duration of a pulse with transfer of energy while said oscillations persist, applying and storing the said transferred energy to initiate second electric oscillations and to maintain said second oscillations for a time longer than the duration of said first oscillations.

5. Radio receiving apparatus, comprising a vacuum tube having a cathode, a grid and a plate, a tuned grid-tuned plate oscillatory network connected to said tube, input means feeding into the tuned grid part of said network, means to bias said tube to prevent oscillations in the absence of signal in said input, a first capacitance and a first resistance in parallel between said cathode and said biasing means, a second vacuum tube having a plurality of electrodes including a cathode, a grid and a plate, second oscillatory network connected to electrode elements of said second tube, means to bias said second tube to prevent oscillations in the absence of signal upon said grid thereof, a second capacitance and a second resistance in parallel between said biasing means for the second tube and the grid thereof, a rectifier having an anode connected-to the high potential side of said first resistance and a cathode connected to the grid of said second tube and to said second capacitance and second resistance, the resistance of said rectifier being less than that'oi said'second resistance and audio output means connected to the plate of said second tube.

6. Radio receiving apparatus, comprising a vacuum tube having a'cathode, a grid and'plate, a tuned grid-tuned plate oscillatory network connected to said tube, input means feeding into the tuned grid part of 'said'network, means to bias said tube "to prevent oscillations in the absence of signal in said input, means connected to be fed by the plate-cathode current of said tube to build upa potential to extinguish oscillations in said network, a rectifier having an anode connected to the high potential side of, said means and a cathode, a second vacuum tube; having a plurality of electrodes including a grid connected to the cathode of said rectifier and a cathode, a second oscillatory network including two electrodes of said second tube, a capacitance and a resistance each having one side connected to the cathode of said rectifier and to the grid of said second tube and the other side operative- 6 1y connected to the cathode of said second tube, the value of said resistance being greater than the resistance of said rectifier, and means to bias said second tube to extinguish oscillations; when the potential on the grid of said second tube becomes less than a predetermined value.

7. Radio receiving apparatus, comprising a vacuum tube having a cathode, a grid and plate, a tuned grid-tuned plate oscillatory network connected to said tube, input means feeding into the tuned grid part of said network, means to bias said tube to prevent oscillations in the absence of signal in said input, means connected to be fed by the plate-cathode current of said tube to build up a potential to extinguish oscillations in said network, a rectifier connected to be biased for operation by said potential, a second vacuum tube having a plurality of electrodes, a second oscillatory network including two of the said electrodes of the second tube, a second means fed by the current through said rectifier to build up on said second means a potential, said second means including an element having an impedance higher than the resistance of said rectifier, means connecting said second means to said second tube'to initiate and maintain oscillations in said second network While the potential on said second means is greater than a predetermined value, and means to extinguish oscillations in said second network when the potential on said second means drops below said predetermined value.

8. Radio receiving apparatus, comprising oscillator means to pass current when oscillating, input means to transfer signal energy to initiate oscillations in said oscillator means, means to prevent oscillation of said oscillator means in the absence of signal energy in said input means, means fed by current passed by said oscillator means to build up a potential to block the oscillator after a predetermined time, a rectifier connected to be biased for operation by the potential on the last mentioned means, a second oscillator means, means fed by current through said rectifier to build up a second potential connected to said second oscillator means to initiate and maintain oscillations in said second oscillator means while said second potential is greater than a predetermined value, and means to prevent oscillation in said second oscillator means when said second potential is less than said predetermined value.

the value of said resistance being greater than. the resistance of said rectifier while passing current, a vacuum tube having a plurality of electrodes including a cathode, a grid and an anode,

means connecting said grid to the high potential side of said capacitance and resistance and to said biasing means, an oscillatory network including two of said electrodes, a second capacitance and second resistance in parallel with each other and in series with the cathode of said tube, a second vacuum tube having a plurality of electrodes including a cathode, a grid and an anode, a second rectifier operatively connected to the high potential side of said second resistance and to the grid of said second tube, means to bias said second tube, a third resistance and a third capaci tance in parallel connected" at one side to said,

rid; and. the. tput o a d; se ond re ifier. and

t he. th r sie 'io; n i s ns e n r. ai second tube, the value of said'third resistance,

being greater than the resistance of said second fi r H111 as n re t a eb m o ci ry ne work clud n wo, e ect o es o a eco tub n udi ou put eans. c nect d to the anode ojsaidsecondtubel i 19. Radio receiving means, comprising arecti r v n i utan out t me s a imed ircuit connectedto said input, means to bias said rectifier to prevent operation thereof below a ed m ne i ut e e a st r sis nc a d a first capacitance in parallel connected in circuit, with said; input means and said output means, the alueof said resistance being greater thantl e resistance of said rectifier while passing: current, avafiuurn tube having. 'a pluralityv of electrodes including a cathode, a grid and an anode, means connecting said gridto the high potential side of said capacitance and resistance to said biasing means, an oscillatory net- Worl; including two. of said electrodes, a second capacitance and second resistance in parallel. with each other and in series with the cathode of-said tube, a second vacuum tube having a plurality of electrodes including a cathode, a grid and'an anodaa second rectifier operatively con-v nectedto the high potential side of said second resistance and: to the grid of said second tube,

means to bias said second tube, a third resistance and a third capacitance in parallel connected at onefsi deto said-grid. and the output of aid second ifi d: at t o h i i a d, hias is etr sai se bed be he. e ua f an thirdhesistance being greater than the r sist ance o f said second; rectifier while pas r nt a p is j cil at ry ne work icc u as, two electrodes of s id second tube, and a dic d anode. o said Output mean were second tubef -.B regeiving p ra us. ompri ing, a;

ct ing n u a o u elemen s. an.

input circuit-responsive to a short signal pulse connected thereto, "means to bias-said rectifier to prevent operationbelow a predetermined sig; nal-level, oscillatory means adapted topass curjrent when oscillating, means fed by current' throughsaid rectifier-tobuild up a potential connected toinitiate and maintain for an oscil later-y condition-in said oscillatory means for a time longer than a signal pulse a unidirectional current: valve connected to be set into operation by. currentthroughsaid oscillatory means, a second oscillatory means, means fed by current through said-valveand connected to said second oscillatory 'means to initiate andmaintain an oscillatory condition in said second. oscillatory means for. a time longer than the duration of said first mentionedoscillatory condition, andoutput means fed by said second oscillatory means.

12 Radio. receiving apparatus, comprising a rectifier, an input circuit and an output circuitconnected thereto; said output circuit includingenergy storagemeans having a predetermined time constant, oscillatory means connected to saidenergy storage means to utilize the stored energy. to. initiate and maintain an oscillatory condition-fora time longer than the time of pas sage ofz'currcnt through saidrectifier in response swe e lfl. Eulse receiving apparatus comprising a first Il QI lly quiescentflselfebloclring oscillator, pulsere e input means operativev toactivatesaid osc llate a s bq q normally quiescentself-bloclu ing' audiggos cillator, and input means for the sec; ond oscillator responsive to the operation of. the

'lator to activate the second oscillator,

id os il ations ne. -b ck ns afte pre'delrmitiedfi ri repe ter.s st mc mpr s g bides.- ing oscilla or, 'a 'circuitfor, receiving pulses from a remotely located pulsing station and for impressing the same on said blockingoscillator for synchronizing the sama'and a pulse transmitter.

under control of saidblocking oscillator.

16 A. pulse repeater system comprising ablocking oscillator, a circuit for receiving pulses from aremotely located pulsingfstai-ion and for. im.- pressing the same on'said blocking oscillator for synchronizing the same, a pulse transmitter under controlof said blocking oscillator, ands signal modulation circuit, for, modulating. the pulses produced bysaid Lransmitten' ARTHUR A, VARELA.

REFERENCES. CITED The following references are of record in the o hi a ent 

